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Jan. 18, 1927.

M. L. NELSON MULTIOFFICE TELEPHONE SYSTEM 3mm Em & kw

IFTL TTlT MEET-L L. Nslsun Jan-.

'1 Sheet s-Sh''t 2 ML. NELSON MULTIOFFICE TELEPHONE sx's'rzm Original Filed Feb. 9. 1921 Jan. 18, 1927.

Jan. 18,1927. 1,614,67

M. NELSON MULTI OFFICE TELEPHONE SYSTEM 0rigina1 Filed Febv 9. 1921 '7 Sheets-Sheet 5 li-men DI Mm L-NEZ5UTL a? fing- Jan. 18 1927. 1,614,678

M. L. NELSON MULTIOFFICE TELEPHONE SYSTEM Original Filed Feb. 9. 1921- sheets-sh't 4 Inu5n ur- Mflfi L. Nslsun Jan. 18, 1927.

M. L. NELSON MULTIOFFICE' TELEPHONE sYs'i'EM 7 Sheets-Sheet 5 Original Filed Feb. 9. 1921 WNN Jan. 18,1927. 1,614,678

M. L. NELSON MULTI OFFI CE TELEPHQNE SYSTEM Original Filed Feb. 9, 1921 vShGetSFShEet 6 Jan. 18,1927.

M. L NELSON MULTIOFFIGE TELEPHONE SYSTEM Original Filed Feb. '9. 1921 7 Sheets-Sheet 7 $i Fr J 3% T I 1? I Patented Jan. 18, 1927.

MARTIN LFNELSON. 0F PARK RIDGE, ILLIHOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

MULTIOFFICE TELEPHONE SYSTEM.

Application filed February 9, 1921, Serial No. 443,688. Renewed March 29, 1926.

referred to anda number of them have been used with some degree of satisfaction by operating telephone compames; The fact 18,

however, that so far as applicant is aware all of the systems heretofore used, or sug-' gested, are either excessively complicated or else they do not perform thedes1red-functions with that degree of eiiiciency or simplicity which is desirable. The present circuits have been designed, therefore, with the shortcomings of prior systems in mind, and with a view to producing an improved system having the maximum simplicity, and capable of doing the required work at high speed and. under uniform operating conditions.

An essential feature of the invention is the B operators sending equipment at the automatic exchange. This apparatus includes a novel sending switch, and a plurality oi't' relay storage devices of new design, together with circuits whereby the digits, corresponding to successively actuated digit keys, are registered on the storage devices, whereby the storage devices successively control the sending switch according to the registered digits, and whereby the entire apparatus is automatically disassoci-' ated from the trunk line in use when the connection iscompleted. There are other features not now specifically mentioned, all of which will he pointed out and fully explained hereinafter with reference 'tothe accompanying drawings.

For an understanding of the circuits, Figs. 1, 2, 3, and d of the drawings should be laid out in order with corresponding lines at the ends thereof in alignment, while Figs. 5, 6, and 7 should be similarly laid out immediately below Figs. 2, 8,- and 4:, respectively. Thedrawingswhen thus arranged show an inter-othcetrunk line connecting a'manual exchange with an automatic exchange, and the associated equipment required to mechanical lish a connection between two subscribers lines such, for example, as the line of the manual sub station A, Fig. 1, and the line of the automatic sub station A, Fig. 4. -The connection, when established, involves a manual cord circuit such as the cord circuit 0, Fig. 1; an inter-office trunk line, manual to automatic, and associated trunk equipment, shown in Fig. 2; a first selector switch D, Fig. 3; a second selector switch such as the second selector E; and a final connector switch such as the connector H, Fig. 4. The apparatus shown in Figs. 5, 6, and 7 constitutes a B operators sender which is used to control the setting of the automatic switches, and which may be temporarily associated with the trunk line for this purpose. Fig. 8 shows a lamp indicating de-.' vice associated with the sender shown: in Figs. 5, 6, and 7.

The equipment shown in Fig. 1 comprising the telephone station A and the associated line equipment atthe exchange, the operators cord circuit 0, andthe A operators head set, is all manual equipment-of wellknown type and on this account will not have to be described.

The inter-foffice trunk line, comprising conductors and 31, is one of a large group of similar trunk lines and extends from the jack J in the outgoing trunk multiple at the A board, in the manual exchange, by way of the B operators position, shown in Fig. 2, to the first selector D, which is shown in Fig. 3. At the B operatorsposition the trunk line is normally open and is provided with a group of relays, whose circuits are shown in full, and whose operation will also be described in the course ofthe general explanation. According tothe usual practice there is a call circuit, or order, Wire circuit, which terminates in the B operators head set at the automatic exchange, and which is multipled in the call circuit keys at the A board in the manual exchange.

The first and second selectors D and E are automatic switches of the well known Strowger vertical and rotary type, such as are in common use in numerous automatic telephone exchanges throughout the country. The connector H is likewise a St-rowger vertical and rotary switch and is similar in construction to the selector switches I) and E. The circuits are arranged, ho ever, for a directive control in lower lefthand corner of Fig. 2, a sending switch indicated by the'reference character S, and including a plurality of associated relays, all of which are shown in Fig. 5, a firstdigit storage device, shown in 6, a second digit storage device, shown in Fig. 7, and third and fourth digit storage devices, which are not shown but are in all respects exactly like the second digit storage device which is shown in Fig. 7. There is also a lamp indicating device, shown in 8 on the same sheet with Fig. 2.

The digitkeys, Nos. 1 to O, inclusive, are ordinary self restoring keys, or push buttons, located-in a single row in front of the B operator, and control the setting of the storage devices. There is also a release key R and a lamp L located in the same row with the digit keys. The sending switch S, in Fig. 5, is a simple rotary switch having two horizontal rows of bank contacts and the two wipers 207 and 208 a ciated therewith. These wipers are adapted to be driven by any suitable form of ratchet mechanism in a forward direction onlyby means of the stepping magnet 205. The cam 298 is mounted on a constantly rotating shaft which is driven by a small motor, or other suitable means, at a speed of about'ten revolutions per sec 0nd: This is the impulse sending cam and -may be common to a number of diiferent senders.

The first digit storage device, shown in Fig. 6, comprises the digit relays 271-270, inclusive, and the live relays 250*25-t, inclusive. The other storage devices are very similar tothe first digit storage device, and

. all of them will'be' described in full hereinafter. h

A little further description otthe apparatus at the B operators position may now be advisable before proceeding with the operation of the system. In addition to the inter-office trunk line, shown in Fig. 2, there may perhaps fifty or more other trunk lines, all extending through the positionby way of their respective associated relay equipments to first selector switches. Tn ad dition' to the operators sender which shown in the'drawings, there'are two or three other senders, making perhaps four al together, and each sender terminates in a devices, respectively.

four conductor trunk line which multi pled at the relay equipments of all the inter office trunk lines. Thus, any sender may be connected with any inter-ofiice trunk line. The local trunk line associated with the sender shown in the drawings, comprises conductors 221-224, inclusive, which conductors are connected .in multiple to contacts of relays, such as the relay 45, associated with the several inter-officetrunk lines. AL though none of the other senders are shown, the local trunk line associated with the sec-- 0nd sender is shown in the drawing at thef right of Fig. 2, and comprises conductors 221' to 224, inclusive. The local trunk lines associated with the other two sendtfrs are similar to the one shown and, therefore, it is believed that the arrangements will be readily understoodIwithout further explanation.

The lamp indicating device, shown inFig. 8, is individual to the sender illustrated, and there is a similar indicating device for each of the other senders. This indicating device comprises a plurality of banks of switch-board lamps, there being a lamp in each bankfor. each of the ten digits. The number of different. banks of lamps will, of course, depend upon the number of digitsin the telephone numbers; for four digit numbers four banks of lamps will, of course,

be required as illustrated in the drawing. The digits to which the lamps correspond are printed on a semi-transparent screen behind which the lamps are located, and these numbers are ordinarily scarcely discernible. lVhen the lamps immediately behind any series of digits are lighted, however, these digits will stand out clearly and may be read by the operator with great facility. The manner in'which the lamps are connected .is exceedingly simple, and on this account the wiring has not been drawn out in detail. It may be explained, 1 however, that one side of all of the lamps is connected to the exchange battery while individual conductors run from the other side of each' lamp to contact springs on the digit relaysof'the several storage devices. Thus, the individual conductors, such as conductor 284, which come from theten lampsiin the. first digit bank are connected to springs of relays 271-270, inclusive, the conductors, such as conductor 335, coming from the lamps of the second. digit bank are connected to contacts of relays '32l-'320, inelusive, of the second digit storage device, while the conductors coming from the lamps in the third and fourth digit banks are similarly connected to the contacts ofihe digit relays in the third and fourth storage The operation of the system in establish- 7 ing a telephone connection will now bG-GX plained, it being assumed for this purpose that the subscriber at sub station A in the manual exchange desires to obtain connection with the subscriber at sub station A in the automatic exchange. The telephone number at sub station A will be assumed as No. 4567. N hen the receiver is removed at sub station A, a circuit is completed over the line conductors 2 and 3 for the line relay 4, which is accordingly energized and lights the line lamp L. This notifiesthe A operator, at whose position the answering jack J appears, that a call has been received and she willrespond by inserting the ans'wering plug of an idle cord circuit, the cord circuit 0 for example, in the jack J. Upon the insertion ot the plug, a circuit is completed over the sleeve conductor thereof which includes the cut ofi' relay 5 of the calling line, and the supervisory lamp L in the cord circuit in series. T 1e cut off relay 5 is accordingly energized and disconnects the line relay 4. The supervisory lamp L would be lighted at the same time were it not or the fact that the receiver is off at sub station A, whose transmitter is now supplied with current from the cord circuit. As a result, the supervisory relay 8 in the ring side of the cord circuit is energized and shunts out the lamp L to prevent it from being lighted. V

The A operator will now throw her key K to listening position in order to obtain from the calling subscriber the number of the party with whom he desires to converse. Having ascertained that the desired number is the No.4567 in the automatic office, the operator will restore her listening key and will depress the proper. call circuit button in order to connect her head set with the call circuit extending to the desired oflice, or exchange. The call circuit button at this particular A operators position, which is associated with the particular automatic exchange in question, is the button P, and when this is depressed the A operators head set is connected directly with the B operators head set in the automatic ofiice. The A operatornow repeats the No. 4567 to the B operator, and this number is registered by the latter operator by means of the digit keys associated with one of her senders as soon as it is received, it being understood, of course, that in the present case the sender which is shown in the drawing is the one which will be used. In registering the number, the B operator will depress the digit keys 4. 5, 6, and 7 in rapid succession and the entire number is completely registered practically as soon as the A operator has finished transmitting it. As soon as the A operator is through talking the B operator will reply with the number of an idle interotfice trunk line. The A operator now inserts the calling plug of the cord circuit in use in the designated jack inthe outgoing with the trunk line.

trunk multiple. Assuming that the trunk line comprising conductors 30 and 31 is the trunk line assigned, the plug will be inserted in the jack J" and a circuit is immediately completed over the two sides of the trunk line in series for the bridged relay 40 at the B operators position. Relay 40 is energizedbycurrent flowing from the cord circuit at the A board and closes a,

circuit for the busy lamp L This notifies the B operator that the A operator has taken the trunk and she will now depress the key K which. is associated with the trunk line in use and also with the sender upon which the desiredv number has been registered in order to connect this sender The sending switch S, Fig. 5, is now operated under the control of the several storage devices in succession and tour series'ot' impluses are transmitted over the trunk line comprising conductors 60 and 61, connecting Figs. 2 and 3 whereby the first selector 1), a second selector, such as the selector E, and a connector, such asthe connector H, are operated in order to complete connection to the desired subscribers line.

The .B operator, having actuated the trunk key K, has doneall that is required of her toward the establishment of the connection and need pay no further attention to it. The sender, upon which the number has been registered, controls the automatic switches without any further attention, and when the last switch has been operated the sender is automatically disassociated from the trunk line and is ready for use in registering ancircuit is completed over conductor 234 for the fourth digit relay 274. Upon energizing, relay 274 prepares a locking circuit for itself at armature 281; connects the grounded conductor 228 to conductor 284 which extends to the No. 4 lamp in the first digit bank of the lamp indicating device, and causes the digit 4 to be immediately displayed; and connects the grounded conductor 288 with the conductor 264 which extends to the lower bank of the impulse sending switch S and there terminates in bank contact 294. The operator depresses the digit key only for an instant and when it is released, relay 274 is held up over the hercinbefore mentioned locking circuit which includes relay 252 and the grounded conductor 226. Relay 252 is accordingly energized in series with relay 274, having been prevented from energizing before by the short-circuiting ground on conductor 234 and at its arma ture 258 closes a circuit for relays 253 and 254 in series, which, upon energizing, disconnect all of the digit relays, 271270, inclusive, from the conductors coming from the digit keys. Relay 274, of course, remains energized over its locking circuit.

Relay 252 also connects ground to the hold ing conductor .223 at armature 260, and at armature 259 connects ground to conductor 285 extending to the second digit storage device, :Fig. 7, thus completing a circuit for rela s-304-and 305 in series. U on ener izin on-energizing, relay 325 prepares a locking circult for itself at 1ts armature 331, con-' nects the grounded conductor 228 to the lamp conductor 335 at armature 333, thereby displaying the No.5 digit in the second digit bank of the lamp indicating device, and connects conductor 388 to conductor 265 at armature 332. The latterconductor extends to the lower bank of the sending switch S and terminates there inbank contact 295. When the No. 5 digit key is released, ground is removed from conductor 235 and relay 325 becomes locked in series with relay 303 over conductor 285. Relay 303 is accordingly energized in series with relay 325 and at its armature 312 breaksthe circuit of re lays 304 and 305, whereupon these relays fall back and disconnect the digit relays 321320, inclusive, from the conductors coming from the digit keys. Relay 303 also grounds the holding conductor 223 at its armature 311, and at its armature 310 grounds the conductor 385 which extends to the third digit storage device, thereby completing a circuit for the relays, corresponding to relays 304 and 305, which connect the ten digit relays of the third digit storage device with the conductors coming from the digit keys.

lVhen the operator depresses theNo. 6 digit key, a circuit is completed over conductor 236 for the sixth digit relay in the third digit storage device and this relay is energized with a result similar to that described in the case of the two previously energized digit relays, and it follows that the digit 6 is displayed in the third digit bank of the lamp indicating device, and a circuit is prepared for grounding conductor 266 which extends to the lower bank of the sending switch S and terminates there in bank contact 296. When the operator releases the No. 6 digit key, the sixth digit relay in the responding toiconductor 385, which extends to the fourth digit storage device, whereupon a circuit 15 completed for a pair of relays 1n sald device, corresponding to the relays 304 and 305 of the second digit storage de- Ground is also placed I vice, these relayshaving the function of connecting up the ten digit relays of the fourth digit storage device to the conductors coming from the digit keys. i 7

When the No. 7 digit key is depressed, the operations which take place at the fourth digit storage deviceare similarto those described in the case of the'other storage devices. The No. 7 digit relay is energized over conductor 237, and this-relay causesthe digit 7 to the displayed at the fourth digit bank of the lamp indicatingdevice and also prepares a circuit. for grounding conductor 267, "which conductor terminates in bank contact 297 of the sending switch S. After the N o. 7 digit key is released, the energized digit relay becomes locked in series with a relay, corresponding to relay 303, which is energized in order to ground the holding conductor 223 and also to break the circuit of the relays which have previously been effective to connect the ten digit relays ofthe fourth digit storage device with the conductors coming from the digitkeys.

From the foregoing it willIbe understood that the fourth, fifth, sixth and seventh digit relays in the first, second,'third, and fourth storage devices,.respectively, are now locked up, with the result that the telephone number 4567 has been displayed on the lamp indicating device, and with the. further result that bank contact 294 of the sending switch S has been grounded, while bank contacts 295, 296 and 297 have been connected with in the last three storage devices, respectively, wherein circuits have been prepared for grounding these bank'contacts also at the proper time. It should be remembered also that the holding conductor 223 has been grounded at each Of the four 7 storage devices. The pilot lamp L, which is located in line with the digit keys of the sender, upon which the number has just been registered, is also lighted inasmuch as it is connected with the grounded holding conductor 223. The function of thelamp indicating device, upon which the .digits .are

displayed as fast asthe y are registered, is V way of grounded conductor 56.

to indicate completed telephone numbers to the B operator with a View to affording her a check on the accuracy of her work. In order to obtain the best results and the maximum speed of operation it is intended that the B operator will register the digits in the telephone numbers as they are transmitted to her by the A operator, from which it will be evident that the digit keys are necessarily operated with great rapidity, and in quick succession. Although an experienced operator soon becomes accustomed to this and will make very few mistakes, there will be times nevertheless when she is interrupted in her work or for some other reason is uncertain whether she has registered the correct number or not, and at such times the lamp indicating device affords a convenient method of at once ascertaining what number has actually been registered. If it is not desired to use the indicating device constantly, a key may be inserted in the battery conductor in order to disconnect the current supply from the lamps, and the key may then be operated whenever it is desired to show up some particular number. In case an inspection of the indicating device should show that a telephone number has been registered inaccurately, the release key It may be actuated in order to energize relay 203 for the purpose of restoring the digit relays of the several storage devices to normal position. The manner in which this is accomplished by the operation of relay 203 will be clear from the subsequent explanation of the restoration of these relays under ordinary circumstances, consequently it will not be necessary to make any detailed explanation of it at this time.

Having completed the registration of the number, the B operator assigns a trunk to the A operator, as previously explained, and as soon as the A operator has taken the trunk, as indicated by the lighting of the busy lamp L the B operator will actuate the trunk key K. By this means a circuit is completed for the upper winding of relay by Upon energizing, relay 45 looks itself to the grounded holding conductor 223 at its armature 52, closes a circuit for the upper winding of relay 44 at armature 51, and at armatures and 53 connects the trunk conductors and 6-1 with the conductors 221 and 222 coming from the sending switch S, Fig. 5. Conductors 221 and 222 are normally connected together at armature 212 and also at armature 214 of relays 201 and 202 of the sending switch S, and it follows, therefore, that a circuit is completed over the trunk conductors 60' and 61 for the line relay 65 of thefirst selector D, Fig. 'Upon energizing, relay 65 closes a circuit for the slow acting release relay 66. The latter relay, upon'energizing, opens a pointin the circuit of the release magnet 72 and prepares a circuit for the vertical magnet in the customary manner.

Relay 44 is operated when the circuit is closed through its upper winding and completes a locking circuit for itself at its armature 48. In addition relay 44 closes a pair of contacts in the trunk conductors in order that when the relay 45 deenergizes, as will occur shortly, the said trunk line may extend continuously through the operators position. When relay 45 is energized, as just explained, the conductor 224 is grounded, being connected with conductor 223 at armature 52, and a circuit is completed for slow acting relay 204, Fig. 5. Upon energizing, relay 204 closes a circuit for slow acting relay 205 at its armature 217 and at its armature 218 disconnects ground from the conductor 228. The latter operation eX- tinguishes the lights in the lamp indicating device, and when the slow acting relay 205 pulls up it opens the normal ground connection to conductor 226 at its armature219 and substitutes therefor a ground coming from the working contact of armature 218 of relay 204. Since relay 204 is already energized and since the contacts at armature 219 are of the make before break type, conductor 226 is held grounded continuously during this operation. In addition to causing the operation of relays 204 and 205, the grounding of conductor 224 produces another result, which is the closure of a circuit for the impulsing relay 202. This circuit is broken at the rate of about ten times per second by the constantly rotating cam 298, and the circuit is accordingly closed the first time the said cam comes into the proper position after'the conductor 224 is grounded. Relay 202 is now intermittently energized and deenergized by the operation of cam 298. At the first energization relay 202 does not open the circuit of the line relay 65 of the first selector D at armature 214 because this circuit is closed also at armature 212 of relay 201. At armature 215, however, a circuit is completed for the stepping magnet 206 of the sending switch S and this magnet is energized. Upon the deenergization of relay 202 the circuit of the stepping magnet 206 is broken and the said magnet retracts its armature, thereby advancing the wipers 207 and 208 one step. The wiper 207 now engages the first grounded contact in its as sociated bank and thereby closes a circuit for the slow acting relay 201 which energizes and prepares a locking circuit for slow acting relay 200. Relay 201 also opens, at armature 212, the shunt circuit which normally renders the impulsing relay 202 ineffective to interrupt the circuit of the line relay of the selector D. The impulsing relay 202 continues to be energized and deenergized intermittently by the operation of the cam 298, and at each energization this relay will separate the two conductors 221 and 222 and will thereby produce a series of. interruptions in the circuit of the line relay 65 of the selector D. At the same time relay 202 transmits a series of impulses to the stepping magnet 206 at armature 215, and. the sending switch S is thus driven synchronously withithe first selector. After four interruptions have been produced in this way,.the stepping magnet 206 willhave been energized four more times, and the wiper 208 willbeadvanced into engagement with the now grounded bank contact 294. A circuit is thus completed for the slow acting relay 200, which immediately energizes, establishes alocking circuit for itself at its armature 210, and'at its armature 211 opens the circuit of'the impulsing relay 202,

thus preventing the transmission, of any 7 more impulsesover the trunkcircuit for the ping magnet itself, the saidstepping magnet will operate in the manner ofa buzzer and the switch will be advanced automatically until wiper 207 arrives at the first ungrounded' contact in its bank which, as shown in thedrawing, is the twelfth bank contact. During this time certain operations are taking place at the first digit storage device which will now be explained.

At the same time that a circuit is com-. pleted. for, relay 200 by the arrival. of wiper 208 at grounded bank contact 294, a circuit is completed by this wiper which extends over conductor 227 and by way of armature 255 and its resting contact torelay 251 at the first digit storage device, thus energizing this relay. As. explained before, the switch S continues to advance its wipers and as soon as wiper 207 reaches its twelfth bank contact, relays 201 and 200 are. deenergized, as:is, explained more in detail hereinafter. Ground is thus removed from conductor 227,

and relay 251- will become lockedin operated position over a circuit which includes relay 250 and the grounded conductor 226. Relay 250 is, therefore, energized with the result that conductor: 227 is disconnected from relay 251 and is transferred by way of conductor 287 to the corresponding relay 302 ofthe second digit. storage device. Further results ofthe energization of relay 250 are the opening of the ground connection at armature 257 to the holding conductor 223 in the first digit storage device (it will be recollected that this holding conductor is still grounded in each of the'other three storage devices) the removal of ground from conductor 288, at. armature 256, whereby ground is disconnected from bank contact 294 in the bank of the sending switch S; and the grounding of conductor 286 at the same armature 256, whereby ground is extended by way of the energized digit relay 32 5 of the second digit storage device, and conductor 265 to bank contact 295 of the sending switch S. The Operations so far described have resulted in the transmission of a series of four impulses to the selector D, or more specifically speaking, the circuit of the line relay 65 of the said selector has been interrupted four-times and in response to these interruptions the selector is operated to raise its wiper to the fourth level, and at l at armature 214. of the impulsing relay 202.

Its circuit having been broken, the slow acting relay 200 also deenergizes after a. brief instant and at its armature 211 againcloses the circuit. of the impulsing relay 202. This relay now begins operating as before and on I its first energization transmits an impulse of current to the stepping magnet 206w-ithout, however, interrupting the switch control circuit over the trunkline, which nowex.- tends through to the second selector E. On the first step of the sendingswitch S, wiper 207 arrives at the thirteenth bank contact and since this contact is grounded? a circuit is completed for the slow acting relay 201 which operates to open the shunt circuit at itsarmature 212 as before. Subsequent energizationsof the impulsing relay 202 now cause the control circuit extendingto the selector E to be interrupted" a plurality of times, while at the same time the stepping magnet 206 is intermittently energized" to drive the wipers of the sending switch. When wiper 208 arrives at the eighteenth contact in its associated bank, which contact is connected in multiple with the bank con? tact 295, a circuit will be completed for relay 200, and this relay is energized as before to open the circuit of the impulsingreuntil the wiper 207 arrivesatthe nextun grounded bank contact,.which is the twenty- V fifth. At the same time that relay 200, is energized, a circuit is completed. by way of conductors 227 and 287 for relay 302 in the second digit storage device and the said re- My 302 is energized. As the sending switch continues its advance, this circuit is broken and relay 302 becomes locked in series with relay 301 to the grounded conductor 285. Relay 301 is accordingly energized and at its armature 306 disconnects conductor 287 from the winding of relay 302 and transfers it by way of conductor 387 to a similar relay in the third digit. storage device. In addition, relay 301 disconnects the grounded conductor 286 from conductor 388, thereby removing ground from the bank contact 295 in the bank of the sending switch S, and transfers it into connection with conductor 386, whereby ground is extended by way of the now energized sixth digit relay in the third digit storage device, to bank contact 296 in the bank of the sending switch, and at armature 308 of relay 301 the ground conncction to the holding conductor 223 in the second digit storage device is broken.

The second series of operations at the operators sending equipment resulted in the transmission of five impulses to the selector E, or rather in the production of five int-erruptions in the circuit of its line relay 90, whereby the switch shaft and wipers are raised opposite the fifth level of bank contacts. Upon the cessation of the series of impulses, the second selector E automatically operates to select an idle trunk leading to a connector switch, such as the connector H, Fig. 4.

When the wiper 207 of the sending switch arrives at the twenty-fifth bank Contact it finds this contact ungrounded, the advance of the switch is stopped temporarily, and relay 201 is deenergized, thus again shunting the impulsing contact at armature 214:. After a brief further interval, the slow acting relay 200 will fall back and again close the circuit of impulsing relay 202, which now begins operating as before, and produces a series of interruptions in the control circuit of the connector H to operate this switch vertically, while at the same time the impulses are transmitted to the stepping magnet 206, in order to drive the sending switch S. It is understood, of course, that the first energization of relay 202 is ineffective to interrupt the control circuit. it will be unnecessary to minutely consider all the operations which take place during the transmission of the third and fourth series of impulses. The third series is terminated by the arrival of wiper 208 at grounded bank contact 296 which causes relay 200 to be energized, inorder to advance the sending switch automatically to the twelfth contact in its bank, and which closes a circu'it over conductors 227, 287 and 387 to the relay in the third digit storagedevice which correspondsto relay 302 of the second digit storage device. Upon the removal of ground from conductor 227 by the further advance ofthe sending switch S, a relay in the third digit storage device, corresponding to relay 301 of the second digit storage device, is energized and various transfer operations take place which result in the removal of ground from bank contact 296 and in the grounding of bank contact 297.

The connector l-ll responds to the third series ofgimpulsesyand its shaft and wipers are raised five steps until they stand opposite the fifth level of bank contacts. No automatic movement takes place at the connector, however, upon the cessation of the series of impulses and further movement of the connector is deferred until-the arrival of the next series of impulses.

When the wipers of thesending switch b arrive at the twelfth set of bank contacts, wiper 207 will find no ground and relays 201 and 200 are accordingly deenergized to again start the operation of the switch. he impulsing relay 202 now begins to step the switch S around as before, and after the first step begins to transmit the final series of impulses over the control circuit to the connector H. This last seics ofimpulses is terminated by the arrival of wiper 208 at the twentieth contact in its bank which is connected in multiple with bank contact 297 and which is, therefore, grounded. When this occurs, relay 200 is energized as usual to stop the transmission of impulses and to ClO'.G- the automatic stepping circuit for the stepping magnet 206 of the sending switch. At the same time conductor 227 is grounded, and a circuit is completed over said conductor and conductors 287 and 387 and thence by way of a similar conductor, in the third digit storage device, to a relay in the fourth digit storage device, which corresponds to relay 302 of the second digit storage device. As the sending switch continues its advance ground is removed from conductor 227, whereupon a transfer relay in the fourth digit storage device, which corresponds to transfer relay 801 of the second digit storage device, is energized. iiince the fourth digit storage device is the last one, it will be apparent that those conductors, corresponding to conductors 365,

and 367. will be omitted, and the principle. result of the operation of'the transfer relay is the removal of ground from the holding conductor 223. Ground has already been removed from this holding conductor at each of the other three storage devices, and it follows that conductor 223 will now be entirely clear of ground. At the same time that conductor is cleared, conductor 22% is cleared of ground also for this conopens the circuit of; the impulsing relay 202 and thus prevents any further operation of the sending switch S at this time. The removal of ground'from conductor 224' also causes the deenergization of the slow actin g relay 204, which opens the circuit of the. slow acting relay 205 at armature 217 and at the same time disconnects ground from conductor 226 at armature 218. As a result of the latter operation, and before relay 205 deenergizes, relays 250, 251, 252, and 274 of the first digit storage device are deenergized. Relay 252, upon deenergizing, opens the circuit of relays 253 and 254 which are thus deenergized also, and also removes ground from conductor 285 at armature 259. By the latter operation relays 301, 302, 303, and 325 of the second digit storage device are deenergized. Relay 3023, upon deenergizing, removes ground from conductor 385 extending to. the third digit storage device, and as a result the corresponding relays in this storage device are deenergized also. In a similar way, the relays in the fourth digit storage device, which have beenlocked up, are deenergized an instant later. The'operators sending equipment, including the four digit storage. devices and the sending switch S, is thus entirely restored to normal positionv and is ready for use again in registering another telephone number.

At the trunk line, Fig. 2, when ground is removed from the holding conductor 223 the locking circuit of relay 45 is broken and thus the relay is accordingly deenergized. As a result the circuit of'relay 44 is broken, but this relay remains locked up to the grounded conductor 56 at its armature 48. By the deenergization of relay 45, the incoming c011- ductors 30 and 81 of the .inter-office trunk line, are connected through the two condensers by way of armatures 47 and 49 of relay 44, and through the normally closed sets of contact springs controlled by relays 45 and 46 to the outgoing trunk conductors 60 and 61, which have been extended, by the operation of selectors D and E and the connector lic ations.

H, to the desired called line. It willbe observed that there is a bridge across the trunk conductors 60 and 61 at the B operators position which includes the impedence coil 43 and upper winding of the electropolarized relay 42. Thus, the continuity of the switch control circuit extending through to the connector H is preserved and the switchesare prevented from releasing. The two windingsof relay 42 are in opposition at this time and consequently this relay is not operated.

The operation of the automatic switches will now be explained alittle more in detail, in order that the entire system may be fully understood without reference to other pub- As previously explained, the control circuit of'the first selector 1) includes the conductors 221 and'222 coming from the sending switch S, and the trunk conductors 60 and 61, and when'the first series of interruptions is produced in this circuit by the intermittent impulsingrelay 2020f the said sending switch, the line relay 65 of the first selector is caused. to retract its armature a corresponding plurality of times. At each retraction of its armature, relay 65 sends a current impulse through the slow acting series relay 67 and the vertical magnet 70 in series, and the vertical magnet is operated to raise the switch shaft step by step until the wipers 80, 81., and 82 stand opposite the fourth level of. bank contacts Relay- 67 is energized in series with the'vertical magnet, and being slow acting retains its armature in operated position. throughout the vertical movement of the switch. At'the first upwardstep, the off normal springs 7 8 are closed and since relay 67 is in operated position a circuit is completed for the stepping relay 68. Upon energizmg, relay 68 establishes a locking circuit for itself at its upper. armature, and at its lower armature prepares a circuit for the rotary magnet 71.

At the end of the vertical movement of the switch, the slow acting relay 67 is deenerupon deenergizes also and again closes its interrupter contact. .The operation now depends upon whether the trunk line terminating in the first set of contacts is busy or idle. If this trunk line is busy, .there will be a ground potential on the test contact engaged by the test wiper '81 and the stepping relay 68 will again be energized, resulting in another closure of the rotary magnet circuit and the advance of the switch wipers into engagement with the second set ofbank contacts, and this operation will continue as long'asthe test wiper 81 continues to engage grounded test contacts. When the first idle iiitrunk line is reached, which we will assume to be the trunk line extending to the second selector .E, the test wiper 81 will find no ground potential on the test contact 84- and the stepping relay 68 will not again be operated. Instead, the switching relay 69, which has heretofore been short circuited, is energized in series with the stepping relay grounds the test wiper 81 at its armature 7 5 inorder to make the selected trunk line busy, and at its armatures 74 and 77 disconnects the trunk conductors and 61 from tacts 83 and 85, conductors 86 and 88, and

armatures 9 1 and 96 and their resting contacts to the upper and lower windings of the line relay 90 of the second selector E.

When the trunk conductors are extended to the selector E, as above described, the line relay 90 is ener ized and closes a circuit tor the slow acting release relay 91. Upon energizing, relay 91 prepares the selector for operation in its vertical movement in the usual manner, and also connects ground to the release trunk conductor 87, thereby establishing a holding circuit which extends by way of said conductor 87, test contact 8 1, test wiper 81, armature and its working. contact, winding of the switching relay 69, interrupter contacts of the rotary magnet 71, off normal'springs 7 8, and the winding of the stepping relay 68 to battery.

The operations just described whereby trunk conductors 60 and 61 have been extended through to the second selector E have occurred in response to the transmission of the first series of impulses by the sending switch S. The automatic rotary movement ot the selector D in selecting an idle trunk line. in the particular level, which.

was selected under the directive control of the sender, takes place during the time interval between the transmission of the first and the second series of impulses. It will so recollected that this time interval is in troduced by the relays 201 and 200, of the sending switch, which are slow acting and which, therefore, require an appreciable length of time to fall back. It may be apprehended that an additional time interval is introduced between each two series of impulses, owing to the fact that the sending switch S is forced to complete its travel from one of its normal positions to the next each time a series of impulses is transmitted, This is true to a certain extent, but the time interval thus introduced is so short as to be inappreciable. The switch S travels over its bank contacts at a rate of about sixty per second when it is advancing its wipers automatically.

hen the next series of impulses come in over the trunk conductors 60 and 61, the line relay of the second selector E is deenergized a plurality of times and controls the vertical magnet 92 to raise the shaft and wipers 100402, inclusive, to the'fifth level, the second digit in the number being the digit 5, as explained heretofore. The operation of the second select r E is precisely the same as that of the first selector D, and consequently it will be unnecessary to consider it in detail, It will be sufficient to say that at the end of the .vertical movement of the switch, the rotary movement is initiated automatically and the wipers are rotated step by step in search of an idle trunk line leading to a connector switch. Assuming that the first idle trunk line en countered is the one shown in the drawing and extending to the connector H, Fig. 4, when the test wiper arrives at test contact 10st it-will find the said test contact unguarded, and the selecting movement of the switch will be arrested. The switching relay 99 is now energized, and the trunk conductors 86 and 88 incoming to the selector are disconnected from the windings of the line relay 90 and are extended by way 01 armatures 94, and 96 and their working contacts, wipers 100 and 102, bank contacts 10 and 105, conductors 106and 108, normally closed contact springs of the back bridge relay 110 to the upper and lower windings of the double wound linerelay111 of the connector H.

@n the extension of the control circuit to the connector H in the above manner, the line relay 111 is energized and completes a circuit for the slow acting release relay 112. Upon energizing, relay 112 prepares the connector for operation in its vertical movement in the usual way and at armature connects ground to the release trunk conductor 107. A holding circuit is thus established which extends by way of the said conductor 107. test contact 104, test wiper 101, and armature 95 and its working contact, to conductor 87 where it joins a previously described holding circuit extending back to the first selector D. The switching relay 99 at the second selector E is connected to the holding circuit the same as was described in the case of the switching relay 69 of the first selector.

VI hen the third series of impulses, corresponding to the digit 6, are transmitted over the control circuit by the operators sender, the line relay 111 of the connector H is momentarily deenergized six times and at each deenergization transmits an impulse of current to the vertical magnet 118 over a path which extends from ground by way 01' armature 12 1 and its resting contact, armature 126 and its working contact, 011 normal springs 121 and 123, winding of the slow acting series relay 113. and the winding or". the vertical magnet 118 to battery. By the operation of the vertical magnet the wipers 152, inclusive, are raised step by step until they stand opposite the sixth level of bank contacts. Relay 113 is energized in series with the vertical magnet 118 and being slow acting holds'up continuously during the vertical operation of the switch. By the operation of this relay; the vertical magnet circuit is preserved intact, notwithstanding the shifting of the off normal ire rotary magnet 119 over the following circuit: From ground by way of armature 124: and its resting contact, armature 126 and its working contact, off normal springs 121 and 122, armature 127 and its resting contact, resting contact of armature and the said armature, armlature 139 and its resting contact, and the winding of the rotary magnet 119 to the battery. By the open ation of the rotary magnet, the wipers 150 152, inclusive, are rotated step by step and are finally brought to rest in engagement with the particular set of bank contacts in which the line ofsubstation A is terminated, these contacts being indicated in the drawings by reference characters 156,1541 and 155. The slow acting relay 116 is energized in parallel with the rotary magnet and remains continuouslyenergi-zed during the rotary movement.- In operated position, relay 116 connects' the test wiper 151 to the winding ot the test relay 115 by means of its armature and at armature 185 closes an alternative point in the circuit of the rotary magnet, to guard against the possibility of having this circuit opened by the operation of the testrelay while the test Wiper 151 is passing over grounded test contacts.

Thetinal series of impulses has now been received, and the connector wipers have been placed in connection with the terminals of the called line. If the line is busy there will be a ground potential on the test con tact 154 and the test relay 115 will be energized. When-this relay operates it prepares a locking circuit for itself at its armature 131, which is completed when the slow acting relay 1 16 falls back an instant later, opens the rotary'magnet circuit at armature 132, and at armature 134 connects a lead from the busy'si-gnalling machine to the lowor side of the line. By this time the relay 45 at the B operators position has been deenergized, the operators sender has been disconnected, and the trunk conductors 30 and 31 have been connected through by way of the condensers to the trunk conductors 60 and 61. respectively, all as previously explained. It will be evident then that an audible busy signal will be transmitted to the calling subscriber in the distant manual exchange. On perceiving the signal, the subscriber will replace his receiver thereby signailing the operator who will pull down the completed for the switching relay 117 which may be traced from the grounded conductor 107 by way of armature 131 and its resting contact, the upper winding of the switching relay 117, resting contact of armature 183 and the said armature, test wiper 151, test contact 1541-, winding of the cut off or switching relay 162 of the line switchC, and winding of the stepping magnet 164 to battery.

Relays 117 and 162 are energized in series over this circuit, and the latter relay effective to clear the line conductors 160 and 161 of their normal. battery and ground connections in the line switch. It may be explained that owing to a mechanical inter-locking device between the arniatures of the switching relay 162 and the line relay 163, the former relay is operated only about half way at this time, and the wipers of the line switch are not connected up.

At the connector I-l, when the switching relay 117 pulls up, it establishes a locking circuit for itself at arn'iature 138, grounds the test wiper 151 at armature 137, opens the rotary magnet circuit at armature 139,

and at armatures 136 and 1410 connects up the two line wipers 150 and 152. By the latter operation a signalling circuit is established whereby ringing current from the generator GEN is interi'nittently projected out over the called line to operate the bridged ringer at substation A, and notify the called subscriber that he is wanted. The return path for the ringing current includes the upper winding of the ring cut off relay 114, and when the called subscribe-r answers this relay is operated. Upon energizing, relay 114 establishes a locking circuit for itself at its armature 129. breaks the ringing circuit at arrnatures 128 and 130, and at the working contacts of these same armatures finally completes the talking connection.

Current is now supplied to the transmitter at substation A through the windings of the double wound back bridge relay 110 which is accordingly energized. This relay is a reversing relay and hasthe well known function of reversing the incoming trunk conductors 106 and 108 as regards their connections with the windings of the line relay 111. It will be recalled now that the circuit of the line relay 11.1 is completed by way of the bridge through the impedance coil 43, and the upper winding of. the electropolarized relay 42 in the trunk equipment at the B operators position, the'operators sender having been disconnected by this time, and the operation of the reversing relay 110, therefore, will reverse the direction of current flowin the trunk line and more particularly in the bridge thereof which includes the upper winding of the saidelectropolarized relay 42. As a result, the two windings of this relay now co-operate and it is able to attract its armature whereby the upper high resistance Winding of relay a is shunted by means of the relatively low resistance impedance coil 41. Relay 40 remains energized, owing to the fact that its lower winding is still connected in the bridge across conductors and 31, and the result of shunting out the upper high resistance winding of this relay is to augment the flow of current sufiiciently to operate the supervisory relay 7 at theoperators cord circuit in the manual exchange. This serves to extinguish the supervisory lamp L and notifies the operator that the called subscriber in the automatic exchange has answered his telephone. The subscribers may now converse as desired.

When the subscribers are through talking, they will replace their receivers. By the replacement of the receiver at substation A, the supervisory relay 8 is deenergized, and the supervisory lamp L is lighted. When the subscriber at substation A replaces his receiver, the back bridge relay 110 in the connector H is deenergized and the direction of current flow in the section of the trunk tot-he right of the condensers is reversed to normal, thereby causing the electropolarized relay 42 to retract its armature. By this operation the upper high resistance winding of relay is again included in the circuit of the supervisory relay 7 at the A operators cord circuit, and this relay is deenergized to light the supervisory lamp L By the disconnect signals thus given the operator, she is advised that the conversation is finished and she will accordingly pull down the connection. When the plug is removed'from the jack J, the circuit over which relay 40 at the B operators position has been maintained energized, is'broken and relay l0 will accordingly fall back and remove ground from conductor 56. This extinguishes the busy lamp L and also breaks the locking circuit of relay 4: 1. On deenergizing, relay 44: opens the trunk line at armatures 17 and i9, thereby clearing the bridge across the trunk conductors and (31. As a result, the line and release relays 111 and 112 of the connector H are permitted to fall back and these relays jointly close a circuit for the release magnet 120, whereby the connector H is restored to normal in the usual manner. Relay 112 also removes ground from the relase trunk conductor 107 and this operation breaks the holding circuit for the switching relays 69 and 99 of the selectors D and E, respectively. These relays are, therefore, deenergized and circuits are completed for release magnets 7 2 and 93 which operate to restore their associated switches to normal position. All the apparatus is thus returned to normal and is ready for use in setting up other connections.

It will be seen from the foregoing that l have devised a simple and efficient arrangement of circuits and apparatus for handling calls between manual and automatic exchanges, introducing a variety of new features which not only simplify and reduce the cost of the equipment, but add to the speed and facility with which necessary duties are performed by the operators.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

What I claim is:

1. In a telephone system, A and B operators positions, trunk lines coming from the A operators position and passing through the B OfjQIltOfiS position to automatic switches, other automatic switches, means for manually connecting a calling line with one of said trunk lines at the A operators position, an operators sender at the B position comprising a progressively movable sending switch and a plurality of storage devices, said sending switch including a contact device, means whereby the B operator can register the digits in the number of the called line on said devices, means for connecting the sender with the trunk line in use, means whereby the sending switch is then controlled by said storage devices successively 'to-t ansmit series of impulses over the trunk conductors by means of said contact device to operate a series of said switches: to connect with the called line, and means for automatically disconnecting the sender when the connection is completed.

2. In a telephone system, A and B operators positions, trunk lines coming from the A operators position and passing through the B operators position to automatic switches, other automatic switches, a call circuit extending between said positions whereby the A operator can transmit a desired ca led number to the B operator, an operators sender at the B position comprising a progressively movable sending switch and a plurality of storage devices, said sending switch including an interrupter, means whereby the B operator can register the digits in the called number on said. devices, u'ianual means at the A operators'position for connecting a calling line with a" particular one of said trunk lines assigned by the li operator over said call circuit, means whereby the B operator can connect said sender with the trunk line assigned, and

means for then automatically operating said sending switch under the control of said storage devices to transmit a plurality of series of impulses over the trunk conductors by means of said interrupter to operate a series of said switches to complete the connection to the called line.

In an operators sender for controlling automatic switches, a set of digit keys, one for each digit, a plurality of storage devices each comprising a set of digit relays, one relay for each digit, means where by the successive actuation of a plurality of digit keys causes the energization of a particular digit relay in each of said storage devices, an impulse sending mechanism, and means for placing said mechanism under control of said storage devices successively.

4. In an operators sender for controlling automatic switches, a set of digit keys, a plurality of storage devices each comprising a. set of digit relays, the cligitrelays of the first device being normally connected with said keys, and transfer relays and circuits effective to disconnect the digit relays of one device from said keys and to connectthe digit relays of another device whenever a digit key is operated and released.

5. In a telephone operators sender for controlling automatic switches, a plurality of storage devices each comprising a set of digit relays, the number of said storage devices being equal to the number of digits in the telephone numbers, a common set of digit keys, and a transfer relay in each storage device except the last for shifting the control of said keys from one storage device to the next. V (i. In an operatofis sender for controlling automatic switches, a plurality of storage devices each comprising a set of digit relays, a common set of digit keys, a transfer relay in each storage device for shifting the control of said keys from one storage device to the next, means for energizing a digit relay in one of said devices when a digit key i-sactuated, and means for energizing the transfer relay in said device when the actuated digit key is restored.

7. In an operators sender for controlling automatic switches, a plurality of storage devices each comprising a set of digit relays, a common set of digit keys, a transfer relay in each storage device for shifting the control of said keys from one storage device to the next, means for energizing a digit relay in one of said devices when a digit key is actuated, a self locking circuit for the energized digit relay including the associated transfer relay, and circuit connections such that current flow through said transfer relay is delayed until the actuated digit key is restored.

8. In a telephone system, a trunk line terminating in an automatic switch, other switches, an operators sender comprising a plurality of storage devices, means for registering a digit in a called number on each of said devices, a holding conductor, means for grounding said conductor at each storage device when a digit is registered, an impulse transmitting mechanism, a trunk relay for connecting said mechanism wit-h said trunk line, a locking circuit for said relay including said conductor, means for operating said mechanism to transmit impulses to a series of said switches under the control of said storage devices successively, and means effective to disconnect ground from the said con ductor at each storage device in turn as soon as the respectivedevices complete their control over said mechanism, whereby the said conductor is finally entirely disconnected from ground and the said trunk relay is deenergized. V

9. In an operators sender for controlling automatic switches, a switch control circuit, a step by step switch, a constantly driven interrupter, a relay intermittently energized by said interrupter, contacts on said relay for interrupting said control circuit and other contacts on said relay for sending V impulses of current to said switch, and means for preventing said contacts from interrupting said control circuit before an effective impulse is sent to said switchby said other contacts. I

1.0. In an. operators sender for controlling automatic switches, a switch control circuit, a step by step switch, a relay and means for closing an intermittent energizing circuit therefor, contacts on said relay for interrupting said control circuit, contacts on said relay for sending operating ii'npulses to said switch, and circuit connections for preventing the said control circuit from being interrupted until said switch has been moved .a definite distance. a

11. In'an operators sender for controlling automatic switches, a switch control circuit, a step by step switch, a relay and means for closing an intermittent energizing circuit therefor, contacts on said relay for interrupting said control circuit, contacts on said relay for sending operating impulses to said switch, the said interrupting contacts being normally short circuited,.ancl means controlled in the movement of said switch for opening said short circuit to permit said relay to interrupt said control circuit.

12. In an operators sender for controlling automatic switches, a switch control circuit, a step by step switch, a relay and means for closing an intermittent energizing circuit therefor, cont-acts on said relay for interrupting said cont-r01 circuit, contacts on said relay for sending operating impulses to said switch, and means controlled in the movement of said switch for opening the ener- .llf)

Lit

gizing circuit of said relay after a definite series of interruptions has been produced;

13. In an operators sender "for controlling automatic switches, a switch control circuit,

a step by step switch, a relay and means for closing an intermittent energizing circuit therefor, contacts on said relay for interrupting said control circuit, contacts on said relay for sending operating impulses to said switch, means controlled in the movement of said switch for opening the energizing circuit of said relay after a definite series of interruptions has been produced, a circuit for automatically driving said switch to a normal position independent of said relay, and means eflective after a definitetime interval for again completing the energizing circuit of said relay in order to produce another series of interruptions.

. 15. In an operators sender for controlling automatic switches, a switch control circuit, a step by step switch, a relay and means for closing an intermittent energizing circuit therefor, contacts on said relay for interrupting said control circuit, contacts on said relay for sending operating impulses to said switch, a set of digit keys, means responsive to the actuation of a digit key for grounding a corresponding contact in the bank of said switch, and a second relay energized over a wiper of said switch when it engages the grounded contact for opening the circuit of said first relay.

16. In a telephone system, automatic switches for connecting a calling and called. line, operator controlled storage devices for registering the digits in the nun'iber of the called line, a visual digit indicator for en abling the operator to check the accuracy of. the registration, and an'inipulse sending device controlled by said storage devices successively to operate a series of said switches to connect said linesJ 17. In a telephone system, automatic switches for connecting a calling and called line, operator cont-rolled storage devices for registering the digits in the number of the called line, a visual digit indicator for enabling the operator to check the accuracy of the registration, an impulse sending device controlled by said storage devices successively to operate a series or said switches to connect said lines, and means for etiacing the number displayed by said indicator while said switches are being operated.

18. In a telephone system, automatic switches for connecting a calling and called line, an operators sender for controlling said switches and comprising operator controlled registering devices tor registering the digits in the number of the called line, keys common to said devices for setting them successively, and a number indicator for enabling the operator to check the accuracy of the registration.

19. In a telephone system, automatic switches for connecting a calling and called line, an operators sender for controlling said switches and comprising operator controlled registering devices for registering the digits in the number of thecalled line,

keys common to said devices for setting them successively, a number indicator comprising groups of lamps, and means for lighting the proper lamps to display the registered number to the operator.

20. In a telephone system, automatic switches for connecting a calling and called line, an operators sender for controlling said switches and comprising operator controlled registering devices for registering the digits in the number of the called line, a number indicator comprising groups of lamps, means for lighting the proper lamps to display the registered number to the operator, and means for extinguishing said lamps when said sender begins to control said switches. I

21. In a telephone system, automatic switches for connecting a calling and called line, an operators sender for controlling said switches, storage devices for controlling said sender and on which the digits in the number of the called line are registered suc cessively and a visual indicator for displaying each digit to the operator as soon as it is registered. 22. In an operators sender for controlling automatic switches, a control circuit over which impulses are transmitted to the said switches. a stcpbystep sending switch for determining the number of impulses transinitted, means For advancing said switch at a slow rate while impulses are being trans mitted, means responsive to a predetermined. movement of said switch for stopping the transmission of impulses, and means for continuing the advance of said switch at a high rate of speed until the same reaches normal position.

23. In an automatic impulse sender, an impulse generating device, spacing means for causing the impulses to be generated in groups, means including an automatic progressively movable switch for determining 

